1. Field of the Invention
The present invention relates to a microchannel plate (which will be referred to hereinafter as MCP) used in an image intensifier, an ion detector, and inspection equipment including the ion detector, e.g., such as a mass spectrometer, a photoelectron spectrometer, an electron microscope, or a photomultiplier tube.
2. Related Background Art
A microchannel plate (MCP) has a plate-like structural body (main body) and is known as an electron multiplier in which a plurality of channels are regularly arranged. FIG. 1A is a partly broken drawing showing a structure of a typical MCP (single cladding structure) and FIG. 1B is a drawing for explaining an example of use of the MCP.
More specifically, the conventional MCP 6 is a thin disk-shaped structural body (main body) containing lead glass as a major component, in which a large number of small-diameter holes 62 penetrating in the thickness direction are arranged except for an annular periphery 61 and in which electrodes 63 are formed on both sides of the structural body by evaporation. The electrodes 63 are not formed so as to cover the entire surface of MCP 6 but formed so as to expose the periphery 61 of MCP 6 in a region of 0.5 mm to 1.0 mm from the outer edge.
In the MCP 6, as shown in FIG. 1B, the input-side electrode 4 (electrode 63) and output-side electrode 7 (electrode 63) are arranged on the front side and on the back side, respectively, and a predetermined voltage is applied between them by a power supply 15, whereby, when an inner wall (channel wall) defining a hole 62 is bombarded by a charged particle 16 such as an electron or an ion incident into the hole 62, the inner wall emits secondary electrons. This process results in multiplying the incident electron or the like. An aspect ratio of channel (=L/D) is given by the length L of the hole 62 serving as a channel, and the diameter D (channel diameter) of the hole 62.
Particularly, in recent years, there are increasing needs for expansion of the dynamic range of the MCP having the above-described structure, with expansion of application fields thereof.